This invention relates to robotic systems. More specifically a robotic system capable of grasping a part from a part racking area, presenting the part to an operation area, optionally repositioning and re-presenting the part to the operation area one or more times and then storing the part back to the racking area.
Robotic systems for part handling are well known in the art. Such robotic systems are typified by the IRB-140 by ABB Robotics. The IRB-140 is a six axis robotic arm. For part handling applications, the IRB-140 is typically configured with an End of Arm Tool (EOAT) mounted to the end of the robot's arm. The EOAT is operable to grab a part and move it from one location to another.
Because robots can move unexpectedly in a rapid, powerful fashion, protective guarding is typically provided. Guarding around the robot prevents a person from entering an area where the robot might strike and injure the person. Typically, access doors into the guarded area are provided and equipped with sensors such that when an access door is open, the robot is prevented from moving.
A common application for robot part handling is CNC Machine tending. CNC Machines typically cut material from a part to form the part into a new shape. Parts can be of an almost infinite variety of shapes and sizes. Parts are typically placed into and clamped securely by a vise or other means to secure the part in the CNC Machine. A vise will typically have provisions for replaceable, machinable jaws. The vise jaws will typically be machined to match the shape of the part as it will be held for a first machine operation. In many cases, the part will need a second machine operation. For the second operation, the part is typically held in the vise using the face of the part that was machined in the first operation. Because the part shape typically changes after the first operation, a second set of jaws, matching the shape of the part after the first operation, held in a second vise, will typically be needed to hold the part for the second operation.
In a CNC Machine tending application, parts are typically placed into a part racking area, within the guarded area of the robot, through an access door. When the racking area has been filled with parts and the access doors secured, the operator will signal the system to start. The part racking area is typically designed to locate each part in a precise location. The robot must be programmed to precisely locate each part in the rack for pickup. The robot's EOAT is typically designed to match the shape of the part so the part can be precisely located for pickup from the part racking area and placed precisely into the CNC Machine vise. In many cases, the EOAT the robot used to place the part for the first operation is not suitable for moving the part from the first operation to the second operation. Additionally, in many cases, a third EOAT must be used by the robot to move the part out of the second operation fixture and back to the part rack. Each robot EOAT is typically custom engineered and typically has a much higher cost than the vise jaws used in the CNC machine. If a new part having different dimensions is introduced into the CNC Machine tending application, new part racking, robot programming, EOATs and CNC machine vises must be engineered.
To manage multiple EOATs, robots are typically configured in one of two ways: multiple EOATs attached to the end of the robot arm or a robot EOAT changer. Multiple EOATs have the disadvantage of adding weight to the end of the robot arm. The extra weight may necessitate a larger, more expensive robot. Robot EOAT changers are lighter in weight but are typically a more costly alternative.
Implementing a robotic CNC Machine tending application can be very expensive. Robotic costs include fencing, doors, and other safety equipment; part racking, multiple EOATs, tool changers, and other equipment needed to hold, pick and place parts. The cost of the robotic equipment is typically similar in cost to the cost of a CNC Machine and vises. However, the cost of engineering to design part racking, EOATs, guarding and programming of the robotic system is typically far higher than the cost of engineering to design and program a human loaded part. Robotics engineers typically cost two to four times as much as CNC Machine programmers.
For a typical CNC Machine tending application, robotic engineering and implementation expenses for an entire system with a single part might range from $20,000 to more than $100,000. Whereas CNC Machine engineering and implementation expense for vise jaws and a single part are typically less than $1,000. Adding a new, dissimilar part to an existing robotic tending application may incur new robotic engineering costs for part racking, EOATs and robotic programming of $5,000 to more than $100,000. In many cases, the setup time to switch between one part and another part in a robotic tending application could take many hours of work by a robotics engineer and be cost prohibitive. Whereas in a modern CNC Machine, setup time to switch between one part and another part is often less than one hour and can be performed by inexpensive trained operator labor.
In some applications, a human cannot replace a robot because of speed, precision or safety requirements. In CNC Machine tending applications, this is not typically the case. CNC Machine tending is typically performed by humans. When making a decision about using a human or a robot in a CNC Machine tending application, cost and return on investment is almost always the key decision point. Yet for most applications, the robotic engineering costs are too high to amortize over the expected life of the part.
Therefore a need exists for a robotic system that can tend a wide variety of parts with minimal engineering costs and a minimum of setup costs for each part to be run. Because most manufacturing facilities employ relatively low-cost CNC Machine programmers and not robotics engineers, the robotic system should be easily adaptable to a wide variety of parts by a CNC Machine programmer with no robotic programming necessary.
An alternative Robotic tending system incorporates a rack system holding parts attached to pallets. The Erowa Robot Compact (ERC) is typical of these systems. Instead of racks holding work pieces, the ERC stores pallets in the system's racks. The operator affixes each part to a pallet and places the pallet into the ERC. All pallets are stored in precise locations in the rack system and have a common interface to the ERC's EOAT. With pallet locations pre-defined and no need to change the EOAT to handle different parts, the ERC overcomes the primary disadvantages of robot tending systems that pick parts directly off of a shelf: no need to create a custom EOAT for each part and no custom programming required to tend different parts into a CNC machine.
However, there are at least two disadvantages to such systems: the cost of labor required to load each part onto a pallet and the cost and storage requirements of the pallets. Pallets typically incorporate custom fixturing to secure each part to the pallet. The cost of each pallet incorporating custom fixturing can range from $250 to more than $1,000. Most parts typically require two different machining operations with two different types of fixtures for each operation. For a system that holds 50 pallets, the cost of fixturing to configure the system to tend 50 of a single part that requires two operations can range from $25,000 to more than $100,000 compared to $1,000 for a typical human loaded part. Furthermore, in this type of system, the operator must load and secure each part to a pallet for machining and then unsecure and unload each part when it is finished whereas in a traditional robot tending system where the robot picks up parts, the operator needs only to place the part in the rack for machining and pull the part out of the rack after machining.
Therefore a need exists for a robotic system that can tend a wide variety of parts with minimal engineering costs and a minimum of setup costs for each part to be run. The labor required to load and unload the system should be minimal. Because most manufacturing facilities employ relatively low-cost CNC Machine programmers and not robotics engineers, the robotic system should be easily adaptable to a wide variety of parts by a CNC Machine programmer with no robotic programming necessary.